The proposed research is designed to advance current knowledge about the psychological processes underlying people's estimates of group norms and their role in individual-level health attitudes and behavior. Where past work demonstrates that social norms strongly influence people's personal health attitudes and behaviors, research on pluralistic ignorance shows that individuals often misjudge group norms. Thus, people's personal attitudes and behaviors may be affected by "norms" that do not actually exist. The proposed studies integrate work on metacognition with work on group perception to examine why people make such social judgment errors. Experiments 1-2 investigate whether individuals use their metacognitive experiences when making inferences about group support for health behaviors. These experiments manipulate participants' feelings of fluency for a norm and assess how it influences their perceptions of group support. Experiments 3-4 focus on the processes that underlie social influence via reference group norms. Where past work suggests that social influence may be a conscious and deliberative process, the current studies hypothesize it can also act automatically. Understanding the processes underlying social norm construction will advance current understanding of social judgment and give insight into how group-level judgments influence individual-level health behavior. [unreadable] [unreadable]